Q-SSC Behavior During Floods in the Isser Watershed, (North-West of Algeria) (original) (raw)
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Hydrological Sciences Journal, 2019
This study was conducted to characterize the hysteresis of suspended sediment concentration (SSC) at different timescales for the Educational and Research Forest Watershed of Tarbiat Modares University, Iran. Hysteresis loops were developed between flow discharge and SSC using data for (i) the whole period, (ii) seasonal, (iii) monthly and (iv) storm-event timescales. The data were collected on an hourly basis at daily and storm-event scales from October 2007 to July 2008. The SSC hysteresis for all the events in the whole study period showed a clockwise A c c e p t e d M a n u s c r i p t 2 pattern, with a flushing behaviour pointing to sudden changes in sediment sources. The results further reveal that the study watershed behaves differently from the viewpoint of hysteresis patterns, with different conditions of dilution and flushing between SSC and flow discharge at different timescales. These result from the complex varying effect of governing conditions on the watershed.
Within agricultural watersheds suspended sediment-discharge hysteresis during storm events is commonly used to indicate dominant sediment sources and pathways. However, availability of high-resolution data, qualitative metrics, longevity of records, and simultaneous multiwatershed analyses has limited the efficacy of hysteresis as a sediment management tool. This two year study utilizes a quantitative hysteresis index from high-resolution suspended sediment and discharge data to assess fluctuations in sediment source location, delivery mechanisms and export efficiency in three intensively farmed watersheds during events over time. Flow-weighted event sediment export was further considered using multivariate techniques to delineate rainfall, stream hydrology, and antecedent moisture controls on sediment origins. Watersheds with low permeability (moderately-or poorly drained soils) with good surface hydrological connectivity, therefore, had contrasting hysteresis due to source location (hillslope versus channel bank). The well-drained watershed with reduced connectivity exported less sediment but, when watershed connectivity was established, the largest event sediment load of all watersheds occurred. Event sediment export was elevated in arable watersheds when low groundcover was coupled with high connectivity, whereas in the grassland watershed, export was attributed to wetter weather only. Hysteresis analysis successfully indicated contrasting seasonality, connectivity and source availability and is a useful tool to identify watershed specific sediment management practices.
Journal of Hydrology, 2004
The concentration of suspended sediment and discharge generated during flood events are not normally homogenous, and the curve representing sediment concentration vs. discharge through time is often a hysteretic loop. Three types of hysteretic loops were found at Arnás, a Mediterranean headwater catchment in the Central Spanish Pyrenees: clockwise (the most frequent), counterclockwise and eightshaped. They are associated with different levels of humidity and rainfall and therefore indicators of different processes of runoff and sediment transport. Clockwise loops are generated under "normal" stormflow conditions, when the catchment is very moist and runoff generation and sediment supply is limited to areas next to the channel (i.e., sediments are removed, transported and depleted rapidly). Counterclockwise curves occur under very high moisture and high antecedent rainfall conditions. In this case, flood propagation occurs as a kinematic wave. Sediment sources are incorporated all over the catchment. In both cases, saturation excess overland flow generates the superficial runoff. The eight-shaped loop (partial clockwise followed by counterclockwise) occurs with low water content. Here, the runoff generation process is supposed to be infiltration excess overland flow, which causes a rapid extension of the contributing areas both near the channel and over the whole catchment.
Hysteresis Effect in Suspended Sediment Concentration in Kutinska River Basin
Serbian Journal of Geosciences, 2021
Suspended sediment Discharge Hysteresis loops. Changes in the suspended sediment load of a river have important impacts on river morphology, sedimentation process, nutrient flux, aquatic ecology. The hysteresis effects show the relationship between the concentration of suspended sediment and the discharge. This relationship can be observed on the basis of data on mean annual values or an individual storm event. This one year study utilizes a hysteresis from suspended sediment and discharge data to assess fluctuations in sediment source location, delivery mechanisms in Kutinska river basin. The hysteresis loops on the Kutinska river are the figure eight shape, which indicates complex conditions in river basin. It contains elements of clockwise hysteresis as well as elements of counterclockwise. The figure eight hysteresis indicates complex conditions in the dynamics and transport of suspended sediment and shows the order of dominant conditions that occur after dry preconditions. Hysteresis analysis successfully indicated contrasting seasonality, connectivity and source availability and is a useful tool to identify watershed specific sediment management practices.
… and the Environment. International Association of …, 1989
The Atchafalaya and lower Mississippi rivers in south Louisiana show the following characteristics: 1) Hysteresis effects are pronounced, especially during high discharge years where the sediment concentration and load maxima precede discharge maxima by several months and show decreased sediment concentrations by the time discharge peaks; 2) The silt-clay and sand components of the suspended sediment operate distinctively; 3) The total suspended-sediment concentration and the suspended silt-clay concentration follow quadratic power relationships; 4) Downstream differences in discharge-sediment relationships are apparent.
Journal of Hydrology, 2015
In-channel processes Hysteresis Sediment transport In-channel storage HEC-RAS Tuul River s u m m a r y Sediment concentration (SC)-water discharge (Q) relations in rivers are typically governed by multiple and relatively complex processes. Due to hysteresis effects, sediment discharges can differ for similar or equivalent water discharges, which causes scatter in empirical datasets and may decrease the predictive power of SC rating curves. Such hysteresis effects must therefore be understood and accounted for to make dependable predictions for river system management. The overall objectives of this study are to develop modelling approaches suitable for reproducing and predicting hysteresis effects at larger scales and to investigate the possible contribution of in-channel processes (erosion and deposition) to sediment concentration hysteresis loops. To investigate relevant field-scale conditions, we develop a one-dimensional dynamic sediment transport model of the downstream Tuul River (northern Mongolia), investigating in-channel processes along a 141 km stretch during a hydrological year. The results show that the present modelling approach can reproduce both anticlockwise and clockwise hysteresis effects. Importantly, in-channel processes alone can cause considerable anticlockwise hysteresis effects without being reinforced by catchment processes such as hillslope erosion. Such specific contributions from in-channel processes introduced data scatter into the sediment rating curves, decreasing their R 2-values from unity to approximately 0.5 to 0.6. More generally, possible changes in the number or magnitude of high-flow events, caused by climatic or other anthropogenic factors, could influence total sediment deposition, which was primarily found to occur during relatively short high-flow events. Such potential changes also have important implications for the possible spreading of polluted sediments.
Environmental Earth Sciences, 2016
Suspended sediment load (SSL) records in streams can be highly variable in time and space, making it difficult to quantify sediment fluxes and to discriminate particular patterns. The deep study on effective factors and their variability in different time scales is, therefore, a vital task. In the present study, the variability of precipitation and streamflow has been analyzed in Gorgan-roud River Basin, Iran in different time scales. Towards this attempt, daily precipitation, streamflow and SSL records spanning during 4 years (i.e. 1982-1985) from the Ghazaghli station situated in the main stem of the Gorgan-roud, were analyzed using Triple Diagram Model. The results indicated that the temporal streamflow and flood frequency variations largely affected the SSL. The results also showed that the pattern of SSL was more apparent by increasing the time span of the recorded data. According to the results, the sediment load in the study station has been affected by different streamflow magnitudes at monthly, seasonal and yearly time scales. According to the results, some 25 % of SSL has been carried out by streamflow probability of 40 % (i.e., 2.5 years of return period), while the transportation of SSL occurred in all ranges of precipitation amount. The amount of SSL moved by less frequent flows and not influenced by precipitation magnitudes, which indicates that the variations of SSL were mainly the result of temporal variations in evaporation rate, soil and vegetation cover conditions, affected precipitation-discharge-SSL relationships.
Journal of Hydrology, 2010
s u m m a r y Streams in intensively used agricultural catchments are frequently characterised by high transport of suspended solids during rainfall events. Due to a high variability in runoff, the sediment concentration relationship during and between different events and various hysteresis effects, instantaneous sediment concentrations and event loads are difficult to calculate. We tested the applicability of turbidity measurements for calculating instantaneous sediment concentrations and loads in a small agricultural catchment in Austria. We calibrated quasi-continuous turbidity measurements using additional water sampling and employed these calibrated sediment concentrations as benchmark sediment concentrations. Four different methods to calculate instantaneous sediment concentrations were tested on 19 events. A generalized rating curve approach resulted in a considerable bias for both event specific sediment concentrations and total sediments loads. Fitting of event-specific rating curves still misrepresented instantaneous sediment concentrations for the different events, but gave load estimations that were in a range of 5% of the benchmark values. Two approaches accounting explicitly for hysteresis exhibited the best fit and provided load estimations that were in a range of 0-1% deviation to the benchmark sediment concentrations. Nevertheless, several limitations to the hysteresis model approach were identified. Testing the various hysteresis effects against other event parameters such as total rainfall amount, maximum rainfall intensity and initial soil water content revealed interactions to these parameters that could predefine parameter values of the hysteresis model approach.
Prediction and Modeling of Flood Hydrology and Hydraulics
Human, Riparian, and Aquatic Communities, 2000
The basic principles underlying the most commonly used physically-based models of the rainfall-runoff transformation process are reviewed. A thorough knowledge of these principles is a pre-requisite for flood hazard studies and, thus, this chapter reviews several physically-based methods to determine flood discharges, flow depths, and other flood characteristics. The chapter starts with a thorough review of linear system theory applied to the solution of hydrologic flood routing problems in a spatially aggregated manner --Unit Hydrograph approaches. The chapter then proceeds to a review of distributed flood routing approaches, in particular the kinematic wave and dynamic wave approaches. The chapter concludes with a brief discussion about distributed watershed models, including single event models in which flow characteristics are estimated only during the flood, and continuous event models in which flow characteristics are determined continuously during wet periods and dry periods.